1. Field of the Invention
The present Invention is directed to a method for manufacturing a radiation detector for a computed tomography apparatus, as well as to a radiation detector manufactured in accordance with the method.
2. Description of the Prior Art
German OS 39 18 843, corresponding to U.S. Pat. No. 4,870,279, discloses a radiation detector for a computed tomography apparatus as well as a method for manufacturing the radiation detector wherein the radiation detector has a linear row of elongated scintillator rods of dense polycrystalline ceramic material with a rectangular cross section, with one end face in communication via a glued fastening with at least one photodetector of a photodetector row.
For manufacturing such a radiation detector, a wafer of the scintillator material is mounted on a temporary base plate and is cut into a series. of barn, with a dicing saw. After mounting lapping shims on the base plate, a reflective coating is applied that completely fills the spaces between the individual bars. The shims and the excess coating are lapped off and the back surfaces of the scintillator bars are polished. A carrier plate is glued to the back surface of the row of bars, with the reflective coating used as the adhesive. Subsequently, the temporary base plate Is lapped off and the interconnected wafer surface and the front surfaces of the bars are polished. The row of bars with the carrier plate is cut to proper size and the base of the linear row is mounted on an integrated circuit photodetector row. Finally, all uncovered surfaces of the scintillator bars are covered with the reflective coating.
Only one slice can be scanned during a computed tomography examination of a subject with such a radiation detector, however, to be able to simultaneously examine a number of slices of the subject in a computed tomography examination of the subject would be advantageous,
U.S. Pat. No. 5,059,800 discloses a planar x-ray detector that has a grid structure of scintillator material, with a photodetector coupled to the grid elements.
An object of the present invention is to provide a radiation detector of the type initially described and a method for the manufacture thereof wherein the manufacturing outlay is reduced.
According to the Invention, a luminophore layer that is preferably composed of ultraviolet-sensitive material is applied onto an adhesive film in a method step. By subsequently introducing the grid-like structure into the luminophore layer up to the adhesive film with an abrasive cutting process or with lasers, it is thus assured that the grid-like structure of the luminophore layer is advantageously retained after the introduction of the structure. A reordering of the grid elements is thus not required, so that, in particular, the manufacturing outlay is reduced in terms of time. After this, a further adhesive film is applied on that side of the luminophore layer lying opposite the adhesive film, and the ultraviolet-sensitive adhesive film is removed by the application of ultraviolet light. A material that Is substantially opaque to light and that preferably reflects the light emerging from the grid elements back is introduced in the space between the matrix elements of the matrix-shaped structure. In the following method step, at least one surface of the luminophore layer is surface-treated to provide good light transmission to a following photodetector. A gridded luminophore layer is thus obtained that can be inspected in view of its properties and potential faults before it is coupled to the photodetector in a further method step. It is thus likewise possible to test the photodetector for functionability before the luminophore layer is coupled to it. Only those luminophore layers and photodetectors that satisfy a predetermined quality criterion are consequently joined. The rejects, and thus the costs, are considerably reduced compared to a conventional method wherein the luminophore layer and the photodetectors are joined before they are tested.